Since I wrote about the status of our cotton crop two weeks ago, very little has changed as far as the weather is concerned. The Missouri Crop Progress and Condition Report for the week ending July 4 gives an update of how the cotton situation continues to deteriorate. Within a week?s time, we went from the condition of 9 percent in the very poor and poor categories to 14 percent. The factor that is responsible for this is the lack of rainfall.
In the Southeast region, 94 percent of our fields are considered to be very short or short of moisture. Northwest region has 95 percent in the adequate to surplus category. The North Central and Northeast regions are 92 and 94 percent, adequate to surplus, respectively.
This report shows that 16 percent of cotton is setting bolls, which is up 13 points from last week. This is 10 days ahead of last year and 3 days ahead of normal. The crop condition is rated as 3 percent very poor, 14 percent poor, 26 percent fair, 54 percent good and 3 percent excellent.
Last week I received an update on the heat units or DD-60?s. The heat is what drives the cotton physiology processes. According to the Portageville data, from May 1 through June 28, a total of 976 heat units were recorded. To put this into perspective, last year on July 15 we only had accumulated 727. In the last six years, the only other year that was less than 1000 units on July 15 was in 2003. Last year, we harvested 927 pounds per acre and in 2003; we had 840 pounds per acre.
One thing that we are confident of is that at this stage of our season, is that we have an earlier crop. We are seeing conditions in June that we normally don?t experience until July or August. One of my concerns is that the minimum temperatures have been higher than we usually experience and that the cotton does not recover much during the night. We had cooler minimum temperatures last week, with none of them over 70 degrees. According to the Weather Channel for Kennett we are not expected to be much above 70 minimum during the next ten days. It would help if we could just get some rain. According to the Weather Channel site for Kennett, we have forecast for isolated or scattered rainfall for nine of the next 10 days. It?s hard for me to put much faith in forecasts since we have had probabilities of 60 and 40 percent rainfall and we didn?t get a drop.
It has been said that the most critical time for water is during the early reproductive stage in cotton. I found on-line the National Cotton Council?s Cotton Physiology Today Newsletter regarding water use in cotton. This can be found at http://www.cotton.org/tech/physiology/cp....
The chart shows that at the first bloom, the water needs of the plant increase drastically. The greatest needs for the plant begin leveling off at the first open boll. During most years in southeast Missouri, rainfall alone cannot keep cotton in a peak condition without supplemental irrigation.
Water is important for a number of reasons. First, it provides adequate turgor or water pressure to cause plant cells to enlarge and grow. A second factor that requires water is the evaporation of water from the plant. The condition that causes the plant to lose the most water is the temperature or the energy from the sun. Wind and humidity can also impact this but temperature is the most important. The bad news is that we still have high temperatures and little rainfall. Non-irrigated cotton does not have the ability to recover at night.
Cotton has been considered by environmental groups to have a large environmental footprint. However, if you look at the water used, cotton's global water footprint is about 2.6% of the world's water use, lower than other commodities (e.g., Soybeans 4%, Corn 9%, Wheat 12%, and Rice 21%). Cotton?s water consumption is in line with that of most other crops.
One of the advantages that we have over many of the third world countries is that we have more irrigation capability and particularly in southeast Missouri we have good clean groundwater. We are the envy of many cotton producing states in that we have alluvial soils and plenty of water. We also have an advantage in that we don?t need to drill as deep to acquire plenty of water.
One observation in non-irrigated fields is that the cotton less than a foot tall is blooming out of the top of the plant. So even with changing conditions and more rainfall, it is doubtful that these plants would recover to have enough fruiting sites to produce a good crop. With cotton under stress, the plants shut down and provide very little growth and will only put enough fruit on the plant to survive. Plants will also change their leaf structure so that it will not lose more moisture.
Some of the irrigated cotton looks good. However, under hot, dry conditions rainfall or irrigation will often cause the plant to shed fruit because of the heat stress. When cotton begins to flower, the Nodes above White Bloom should be 8- 11. I can remember plant mapping and averaging only 6 due to drought stress. The cotton was under stress most of that summer and the final yields were a reflection of that. With our dry conditions, I will be waiting to see the USDA estimate for yield for all of our cotton states that comes out in the August edition of the USDA?s Cotton and Wool Report.
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Dr. Michael R. Milam is an agronomy specialist and county program director with University of Missouri Extension in Dunklin County.